A shape memory alloy actuator using Peltier modules and R-phase transition

This paper describes the development of a novel shape memory alloy (SMA) actuator with high frequency responses. By applying Peltier modules as heat pumps for heating and cooling of SMAs, the actuator is expected to have higher frequency responses comparing with conventional ones. Thermomechanical properties of the actuators; such as the deformation of SMAs and recovery forces generated during the phase transition of SMAs, were investigated first. Then, response tests of the actuators were carried out in the complete thermal cycles for cases with and without Peltier modules respectively. Based on results from numerical simulations and experiments, the transient behavior of the actuator subjected to continuous actuations has been discussed. The results show that the actuator has dramatically enhanced frequency responses. In cases where the heating and cooling are controlled by electric current sequences, the thermal instability of the actuator occurs due to the accumulation of Joule heat in Peltier modules. Therefore, a proportional plus integral plus derivative (PID) action is employed to control the temperature of the SMA, it leads to the stable actuations with the frequency responses up to 0.5 Hz.